treemanifest: further optimize treemanifest.matches() The matches function was previously traversing all submanifests to look for matching files, even though it was possible to know if a submanifest won't contain any matches. This change adds a visitdir function on the match object to decide quickly if a directory should be visited when traversing. The function also decides if _all_ subdirectories should be traversed. Adding this logic as methods on the match object also makes the logic modifiable by extensions, such as largefiles. An example of a command this speeds up is running hg status --rev .^ python/ on the Mozilla repo with the treemanifest experiment enabled. It goes from 2.03s to 1.85s. More improvements to speed from this change will happen when treemanifests are lazily loaded. Because a flat manifest is still loaded and then converted into treemanifests, speed improvements are limited. This change has no negative effect on speed. For a worst-case example, this command is not negatively impacted: hg status --rev .^ 'relglob:*.js' on the Mozilla repo. It goes from 2.83s to 2.82s.